Gas-shielded metal-arc welding



United States Patent GAS-SHIELDED METAL-ARC WELDING Donald M. Yenni, Williamsville, and Kenneth L. Thomas,

Kenmore, N .Y., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Jan. 13, 1954, Ser. No. 403,934 8 Claims. (Cl. 21974) This invention relates to gas-shielded metal-arc welding and, more particularly, to shielded-inert-gas-metalare or sigma welding with relatively high-current density like that proposed by Muller et al. No. 2,504,868 and Kennedy 2,532,410.

Generally, in sigma welding the shielding gas is argon or helium. Recently, as disclosed in the application of R. T. Breymeier, Serial No. 210,397, filed February 10, 1951, in sigma welding carbon steel, it has been found beneficial to use argon containing some oxygen such as 2-5%. It has also been proposed to use a mixture of helium and argon, Patent No. 2,591,926, as the shielding gas for non-consumable or refractory metal electrode arc welding in which the electrode is tungsten or thoriated tungsten. But it is impossible to predict beforehand that such proposal for refractory-electrode inert gas-shielded arc welding would be suitable also for gas-shielded consumable electrode metal-arc welding.

In an investigation of various shielding gases and gas mixtures for high-current density sigma Welding of carbon steel, we have discovered that wholly unexpected improvements in arc stability and weld bead shape are obtained with a shielding gas consisting of helium, argon and oxygen. For example, a shielding gas composed of a mixture of 67% helium, 31.5% argon and 1.5% oxygen produces a quiet, spatter-free arc, resulting in a very smooth weld bead deposit. We have established that for sigma welding carbon steel, the most suitable shielding gas is one composed of 60% helium and 39% argon 2,958,756 Patented Nov. 1, 1960 and 1% oxygen. Satisfactory results are obtainable when the shielding gas consists of up to 3% oxygen, 40 to helium and the balance argon for sigma welding carbon steel with direct current reverse polarity (DCRP).

According to our invention in the case of sigma welding carbon steel with direct current straight polarity (DCSP), the shielding gas should be relatively dry and contain from 3 to 5% commercially pure oxygen, 70% commercially pure helium and the balance commercially pure argon. 1

Most of the following performance data were secured in sigma welding single pass beads on one-quarter inch thick carbon steel plate with an electrode of one-sixteenth inch diameter welding wire which is'sold by the Linda Air Products Company as No. 32 CMS. Such wire contains about 0.12% carbon, LOO-1.20% manganese, 0.25% silicon, 0.36% chromium, not more than 0.015% sulphur, and the balance iron.

Data are given in Table I below for sigma welding operations using various helium-argon mixtures and heliumargon-oxygen mixtures containing 1, 3 and 5% oxygen. Data obtained with argon, helium, 5% oxygen-% helium, and 5% oxygen-95% argon mixtures are included for comparison. Beads were made at 25 and 50 i.p.m. with direct current-reverse polarity and at 25 i.p.m. with direct current-straight polarity power. A welding speed of 25 i.p.m. was selected since this representts "the maximum speed for producing acceptable welds on inch thick steel plate with pure argon and is also about the maximum speed for hand welding methods. Although arc current was substantially constant (350 amperes) for a given welding speed and polarity, some changes will be noticed in are operating voltage. The voltage for most satisfactory operation with each shielding gas mixture was selected.

The test beads were intended to have penetration somewhat greater than half the plate thickness or 0.125 inch, and a bead width-to-height ratio of four or more. A desirable dilution is 50% or greater. Dilution is the ratio of melted base metal area to total melted area on the bead cross-section. These conditions apply to double pass, square butt welding.

TABLE I (Part I) Shielding Gas Composition Wire Weld He, Feed Ht., Peuet., Width,

No. per- Rate, In. In. In. W/H

cent A, O, AreD.C. i.p.m.

perper- R.P., cent cent Volts 0 0 27 215 .145 390 3. 5 40 60 0 30 220 105 .170 425 4.0 60 40 0 28 260 .080 150 510 6. 4 100 0 0 32 285 .095 .165 550 5.8 0 95 5 27 215 070 .130 .480 6. 9 95 0 5 29 255 .080 210 600 7. 5 25 74 l 28 165 .080 .125 515 6. 4 4O 59 1 28 185 070 525 7. 5 50 49 1 28 185 080 120 500 6. 3 60 39 1 28 200 .085 500 5. 9 70 29 1 30 210 080 520 6. 5 80 19 1 31 235 075 560 7. 5 25 72 3 28 165 .070 .125 500 7. 2 40 57 3 28 .070 110 470 6. 7 50 47 3 28 070 120 495 7. l 60 37 3 28 200 .070 125 .495 7. 1 70 27 3 28 210 080 145 480 6.0 50 45 5 28 225 .070 135 .490 7.0 60 35 5 28 230 075 .140 .495 6. 6 70 25 5 28 235 070 150 505 7. 2

TABLE I According to our invention the best shielding gas com- (Part II) positions for use under established sigma welding conditions should contain 1% oxygen, from 40 to 70% helium and the remainder argon, such as the weld made spatter Surface with 1% oxygen-70% helium- 9% argon. This weld may be compared with the weld made under similar op- Ripplei erating conditions with oxygen-argon. Stable are be- 50 Do. havior and smooth weld bead surface are also secured g; 25 except for Spawn using shielding gas compositions with 3% and 5% oxy- 53 ppled. gen. The higher oxygen concentrations are not as satis- Zg factory because of increased oxidation of the weld sur- :2 Sm g face. The data in Table I show an increase in penetra- 50 tion and melted metal area with increasing helium con 2% ggan centration in the shielding gas.

p Addition of 5% oxygen to pure argon increased di- 28 g g b lution, improved bead cross-section and increased are 49 stability. Similar improvements, however, are not ob- 22 gg tained by adding 5% oxygen to pure helium. Arc stabil- 57 ity and spatter remain essentially constant with no change 28 ggin dilution. Increased penetration and a greater ratio of weld width-to-height are secured.

Butt welds were made using two-pass technique on ggiigggiiggQggfig; 9 prepared 60 double-V, sharp-nose plates and on square- Filler 1 OMS diameteredged plates. As found in the past, sigma welding be- 2?: g g ing-53 3355 33 15? inside diameter) gas havior under actual welding conditions correlated well .411 datataken from weld beads-one pass. with results of bead tests. The welds were made on The weld results in the first group of Table I indicate thick Steel Plates at f sp ed of 25 i.p.m. using clearly the improvement in bead cross-section obtained dlametfir N CMS wlre; reverse f Welds by the addition of helium to argon. This is shown by shleldmg gas obtamed jfrom a cyhndar of increased ratio of head width to height and, while omitted mlxed cofltt'ilmng 53% f 46% argon and 1% from Table I, by increased dilution. Equally satisfac- Smce hfgher F tory bead cross-sections are obtained with 5% oxygena Wlth stFalght polarftya the sh 1e1dm'g gwmlxture 95% argon, and with 5% 0Xygen 95% helium. The used for making the stralght polarity welds was 70% 5% oxygen-helium mixture is not satisfactory, however, hellum 25% argon and 5% oxygen because of excessive spatter and poor arc stability; nor 35 Results of f welds ,ondltlons are is the arc in the O2 A2 mixture as Stable as in the listed below. Satisfactory duct1l1ty 1s indicated by the ternary mixture. Spatter difliculties are also encounf bend test and radlographs Showed no tered using helium-argon mixtures with helium concen- AS 111 the weld F K good rations of 60% and mom b1l1ty was encountered during weldlng and the f nished Performance with various argon-helium ratios and 40 welds were smooth 5 regulal} t' q oxygen concentrations of 3 and 5% are shown in the welds showed sat sfactory d1lut1on, a desirable ratio third, fourth and fifth groups of weld i T bl 1 1 of nugget w1dth-to-he1ght and generally desirable shape. tion and bead width-to-height ratio show that most of WELDING CONDITIONS these welds have satisfactory cross-sections. Arc operation with such mixtures is remarkably stable and little spatter is experienced with any helium-argon-oxy- Plate Ed 8 1 Pass 211d a gigs gen mixture containing 70 helium or less. Thus, the preparmin Polarity Elonga. addition of oxygen to helium-argon mixture increases are p Volts p- Volts on; stability and reduces spatter. Smoothness of weld sur- Perceni face and arc stability are considerably better than that 600D m V of conglparable 1ljaelads mgde withhoxygenf-argon. The iligtsight 51313 25? 300 28 330 28 DCRP 35 crease are sta iity an smoot ness 0 operation ma e 1 P the use of helium-argon-oxygen mixtures ideal for hand figdflifi vnr- 350 28 350 28 DCRP 40 sigma welding operations, where high welding speeds are tight joint 350 26 390 27 DOS? 30 not required.

TABLE II DCSP-25 i.p.m. welding speed 7 Shielding Gas Composition Arc Wire Feed Ht., Penet., Width, Weld No. Rate, In. In. In. W/H

e, A, 0,, Amp Volts i.p.m. Percent Percent Percent 0 100 0 350 30 330 .115 .050 .500 5.2 40 50 0 a 335 32 335 .115 .045 .490 4.2 00 40 0 330 as 320 .105 .030 .405 4.7 100 0 0 335 32 330 .095 .050 .590 0.2 0 05 5 350 20 300 .100 .070 .450 4.5 05 0 5 350 48 575 .125 .100 .500 4.0 50 40 1 330 30 370 .155 .045 .315 1.0 29 1 550 21 430 .135 .045 .455 3.4 50 41 a 350 as 350 .130 .080 .405 3.1 70 27 5 350 as 330 .105 .080 .430 4.1 50 45 5 350 28 330 .100 .095 .440 4.4 70 25 5 350 28 330 .100 .105 .485 4.8

DCSP-25 i.p.m. welding speed The minimum operating current for a stable arc with a given welding rod and shielding gas are important fi ma Dilution, spatter Bead commercially and can be determined visually by observ- I\o. Sq. In. Percent mg the current at which individual drops appear in the A149 33 Irregular, shallow. arc. At this point, unstable are performance generally .057 30 D0. appears. Observations were made with various combina- 28 iggg tions of shielding gas using ,6 diameter No. 32 CMS .051 37 Regular, edges scalloped. wire with direct current reverse polarity and an arc :gg is gg umrmmi Shallow shielding gas flow rate of 100 c.f.h. The data summar- .055 20 High and narrow. ized below show that mixtures, of argon-helium-oxygen 25 am: penetramon made are almost as effective as are shielding gas containing 5% .054 36 -do- Uniform but high. oxygen and the balance argon, in lowering the minimum 1395 2% 33:38:13: Operating current- .074 4a Do. TABLE IV Desired penetration 0.l25 in.

Base p1ate=%-in. O.R. steel (killed). Shielding Gas Composition Current at Arc Filler wire=32 CMS kin-1n. diameter. Which Are Potential,

Gas fl0w=100 c.f.li. total through a #12 inch inside diameter) gas cup Became Errat- Volts All data taken from weld beads-one pass. He Argon 01 lo (Amperes) Although all of the straight polarity welds lacked v penetration, use of helium-argon-oxygen mixtures cong g 3 58 taining 5% oxygen yielded beads with somewhat greater 95 1 5 210-220 28 dilution and penetration than that of beads shielded 8 8 280-310 30 250-200 28 with 5% oxy-argon. Spatter was present but not as 00 0 240-200 28 bad as that observed with 5% oxygen-argon arc shield- 28 i 323 2: ing gas. These comments are based on data in Table 5 5 2404 23 II comparing welds No. 66 and 67 with weld No. 89. 45 5 230-240 23 Beads made with helium-argon, helium-oxygen, 5% oxyargon, and pure argon had little penetration, poor crosssection shape, bad spatter and erratic arc behavior.

Tabulated below is information secured with motion pictures of sigma welding with some of the shielding gas mixtures discussed in this report. The pictures were taken at 10,000 frames per second on weld beads made on %-inch thick steel plate at 25 i.p.m. using M inch No. 32 CMS welding wire with reverse polarity direct current as indicated in Table I. The photographs showed a stable arc in the pure argon, the argon-oxygen and the helium-argon-oxygen shielding gas mixtures, confirming visual observations and correlating with spatter for- According to our invention for sigma welding the oxy-argon-helium arc shielding gas mixture preferably should be relatively dry, i.e. contain not more than 10 grains of moisture per 1000 cubic feet and preferably less than 7 grains/ 1000 cubic feet.

The invention is equally suitable for welding stainless steel. For example, Table V below sets forth data obtained by sigma welding inch thick stainless steel (type 304) plates with inch welding wire (type 304) at a welding speed of 25 inches per minute using DCPR welding current.

TABLE V (Part I) Shielding Gas Composition Arc i virg Weld Bead Measurement ee Weld No. Rate,

He, A, 0 Volts Amps i.p.m Ht., Penet., Width, W/H Percent Percent Percent In. In. In.

mation. Furthermore, the metal transfer drop rate was TABLE V much higher in the stable arcs. Arc shape varied from a (Part II) ball or cylindrical geometry in helium and helium-oxygen shielding gas to a cone or trumpet n argon, sigma argon wem N0 Area Dilution, spam, su f and helium-argon-oxygen. The estimated area of cover- Sq. In. Percent Condition age on the base plate by the intermediate arc zone is listed in order of increasing size: helium, helium-oxygen, 33 Ngi e Elgtllent.

s sigma arson, s ygen. I080 5510 'iiiedrhiliii Fair.

.085 50.6 None Do. TABLE III .079 58.2 do D0. o illfiitifii Table V shows that welding according to the invention Spatter Arc Behavior fer, Bate, of stainless steel is quite satisfactory.

Drops] i.p.m. W 1 He A 01 SW e c aim.

l. A shielding gas for direct current straight polarity 100 None" stab}?! coneghaped ML 150 215 sigma welding of metal selected from the class consisting 100 Bad Erratieball-shaped are; 25-5 285 of carbon steel and stainless steel, composed of a relaoccasional shorting.

5 Cylindrical hape 4H0 255.310 tively dry mixture containing helium, 25% argon ratio.

95 5 None Stable, cone-shaped are; 300 215-250 70 and 5% i i gequentballoomng of 2. A shielding gas composition for direct current re- 70"" 29 1 None" Stable, trumpebshaped 400 210440 verse polarity high current density sigma welding of metal arc, shorter than 5% selected from the class consisting of carbon steel and gfigfi a'g stainless steel, consisting of 60% helium, 39% argon and 1% oxygen.

3. A shielding gas for sigma welding which is composed of a relatively dry mixture of oxygen, helium'and argon, containing 40-70% helium, 1-5% oxygen, and the balance argon.

4. Process of gas-shielded metal-arc welding which comprises striking an are between the Work'and a fusible metal electrode, feeding such electrode toward such work at a relatively rapid rate as molten metal is transferred therefrom to the work through such arc, and shielding the arc and adjacent metal with a gas stream consisting of a mixture containing 40-70% commercially pure helium, 1-5% commercially pure oxygen and the balance commercially pure argon.

5. Process as defined by claim 4, in which the work and electrode are composed of carbon steel.

6. Process as defined by claim 4, in which the work and electrode are composed of stainless steel.

7. A shielding gas for sigma welding stainless steel, which is composed of a mixture of 1% oxygen, 16-29% argon and the balance helium.

8. Sigma welding which includes the step of protecting the welding arc with a stream of gas consisting of a mixture of 1% oxygen, 16-29% argon and the balance helium.

References Cited in the file of this'patent UNITED STATES PATENTS OTHER REFERENCES Arc Welding in Controlled Atmospheres, by Doan and Smith, pp. 1108-1168, in March 1940 Welding Research Supplement. 

1. A SHIELDING GAS FOR DIRECT CURRENT STRAIGHT POLARITY SIGMA WELDING OF METAL SELECTED FROM THE CLASS CONSISTING OF CARBON STEEL AND STAINLESS STEEL, COMPOSED OF A RELATIVELY DRY MIXTURE CONTAINING 70% HELIUM, 25% ARGON AND 5% OXYGEN. 